EP0653069B1 - Apparat und verfahren zum messen von feuchtigkeit - Google Patents

Apparat und verfahren zum messen von feuchtigkeit Download PDF

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Publication number
EP0653069B1
EP0653069B1 EP93916068A EP93916068A EP0653069B1 EP 0653069 B1 EP0653069 B1 EP 0653069B1 EP 93916068 A EP93916068 A EP 93916068A EP 93916068 A EP93916068 A EP 93916068A EP 0653069 B1 EP0653069 B1 EP 0653069B1
Authority
EP
European Patent Office
Prior art keywords
electrode
antenna means
casing
electrodes
measuring
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP93916068A
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English (en)
French (fr)
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EP0653069A1 (de
Inventor
Fali Minocher 32 Highfield Park Dadachanji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GE Protimeter Ltd
Original Assignee
Protimeter PLC
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Filing date
Publication date
Application filed by Protimeter PLC filed Critical Protimeter PLC
Publication of EP0653069A1 publication Critical patent/EP0653069A1/de
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2635—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells

Definitions

  • This invention relates to an improved method of and device for measuring the moisture content of a material.
  • US-A-4468610 discloses apparatus for measuring the moisture content of test pieces of gypsum board in which the capacitative impedance to a radio-frequency signal presented by an antenna disposed adjacent such a test piece is measured to provide an indication of the moisture content of the test piece.
  • a method of measuring the moisture content of a mass of material comprising providing antenna means, arranging said antenna means in a predetermined position relative to a surface of said mass and measuring the radio frequency impedance of said antenna means, characterised in that said antenna means is constituted by a first and a second electrode, said first electrode being disposed at a location at or adjacent said surface of said mass and said second electrode being disposed at a location remote from said first electrode and from said mass, and in that said impedance measured is the free-field radio frequency impedance between said first and second electrodes.
  • a device for measuring the moisture content of a material comprising antenna means, means for applying a radio-frequency voltage signal to said antenna means, and means for measuring the radio-frequency impedance of said antenna means, characterised in that said antenna means is constituted by a first and a second electrode, said means for applying radio frequency voltage is arranged to apply said voltage between said electrodes; and said means for measuring is arranged to measure the free-field radio frequency impedance between said electrodes and in that said device comprises an elongate body having said first electrode at one end of said body and said second electrode at a position in said body spaced from said one end and from said first electrode.
  • the device comprises an elongate body 10 defined by a plastics casing having mounted within it adjacent one end, a first electrode A and further having mounted within it, adjacent the flat lower wall of the casing, a second electrode B, which may, for example, take the form of a flat metal sheet or foil.
  • the electrodes A and B are connected with circuitry (not shown) within the casing, for applying a radio frequency voltage between the electrodes A and B, the electrodes being otherwise electrically isolated from one another.
  • the circuitry within the casing is also arranged to drive a display 12 (such as a galvanometer or a LCD display) and to provide via said display, a visual indication of the rf impedance between the electrodes A and B.
  • the radio frequency field emanating from the front end of the instrument i.e. the end at which electrode A is disposed
  • the front end of the instrument is placed against that surface with the longest dimension of the body 10 extending substantially normal to such surface so that the electrode B is spaced substantially from that surface.
  • the electrode A is again very weakly coupled with electrode B so that again no reading is obtained with the device switched on.
  • the water within the material acts to transmit the radio frequency signal allowing the moisture-containing material to act as an emitting aerial re-radiating the rf field to the electrode B in the lower half of the instrument, normally through the body 10.
  • No part of the electrodes A or B or indeed any part of the electronic circuitry is in direct electrical contact with the material being tested.
  • the "coupling" between the electrodes and the moisture-containing material is entirely made through radio frequency transmissions capable of passing through electrically insulating materials like plastic. This mode of measurement predominantly measures the mass of water in front of the instrument which in certain circumstances is a decided advantage.
  • Figure 2 shows a comparative reading of several layers of wet film interleaved with an insulation material such as a film of pvc.
  • the quantity plotted along the Y-axis is admittance (i.e. the reciprocal of impedance), whilst the number of layers is plotted along the X-axis.
  • the transfer electrode indicated at 16 in Figure 3, when fitted, provides, at the front end of the device, below the rounded or bevelled front end of the casing proper, a second, similarly rounded or bevelled forwardly facing surface whereby, when the front end of the instrument fitted with the transfer electrode is held against a flat surface of material to be tested, the rounded or bevelled front end of the casing proper can make substantially line contact with said surface along a first line and the rounded or bevelled forwardly facing surface of the transfer electrode can make substantially line contact with said surface along a parallel line below the first line.
  • transfer electrode is applied for convenience to the item 16 in its entirety, but it will be appreciated that it is unnecessary for the item 16 to be electrically conductive in its entirety. Indeed, it is envisaged that the item 16 will comprise a plastics outer shell with electrically conductive foil extending over the surface which, when the item 16 is fitted lies immediately below the lower wall of casing 10, below the electrode B, such foil extending, within the shell at least to the location directly behind the peak or ridge of the bevelled front part of such shell which is to engage the surface to be tested.
  • the arrangement is such that, with the transfer electrode 16 fitted, there is a sufficient dielectric gap, between the electrode A and the conductive foil at the front end of the shell, for the rf coupling between such foil and the electrode A to be negligible when the front ends of the device and electrode 16 are not engaged with the surface of a body of damp or otherwise electrically conductive material.
  • the base of the instrument is now electrically rf coupled to the active area adjacent to the normal working tip of the instrument.
  • the double-ended instrument now acts as a near-field measurement device which is inherently more sensitive to water layers close to the sensing elements.
  • the preferred embodiment of the device thus comprises a single instrument which can normally measure moisture deep within a structure using the rf free-field technique but which, by fitting the transfer electrode described above, can also be used to make near-field surface measurements.
  • the devices described with reference to the drawings measure the free-field impedance between the electrodes, in general it will be preferably for the display 12 to be calibrated in terms of moisture content.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Claims (6)

  1. Verfahren zum Messen des Feuchtigkeitsgehalts einer Materialmasse, umfassend Bereitstellen eines Antennenmittels, Anordnen besagten Antennenmittels in einer vorherbestimmten Position relativ zu einer Fläche besagter Masse und Messen der Radiofrequenzimpedanz besagten Antennenmittels, dadurch gekennzeichnet, daß besagtes Antennenmittel aus einer ersten Elektrode (A) und einer zweiten Elektrode (B) aufgebaut ist, wobei besagte erste Elektrode (A) an einer Stelle an oder benachbart zu besagter Fläche besagter Masse angeordnet ist und besagte zweite Elektrode an einer Stelle entfernt von besagter ersten Elektrode und von besagter Masse angeordnet ist, und daß besagte gemessene Impedanz die Freifeldradiofrequenzimpedanz zwischen besagter ersten Elektrode und besagter zweiten Elektrode ist.
  2. Vorrichtung zum Messen des Feuchtigkeitsgehalts eines Materials, wobei die Vorrichtung ein Antennenmittel, ein Mittel zum Anlegen eines Radiofrequenzspannungssignals an besagtes Antennenmittel und ein Mittel zum Messen der Radiofrequenzimpedanz besagten Antennenmittel umfaßt, dadurch gekennzeichnet. das das Antennenmittel von einer ersten Elektrode (A) und einer zweiten Elektrode (B) aufgebaut ist, daß besagtes Mittel zum Anlegen einer Radiofrequenzspannung angeordnet ist, um besagte Spannung zwischen besagten Elektroden (A, B) anzulegen, und daß besagtes Mittel zum Messen angeordnet ist, um die Freifeldradiofrequenzimpedanz zwischen besagten Elektroden zu messen, und daß besagte Vorrichtung einen länglichen Körper (10) umfaßt, der besagte erste Elektrode (A) an einem Ende besagten Körpers (10) und besagte zweite Elektrode (B) an einer Position in besagtem Körper (10) räumlich getrennt von besagtem einen Ende und von besagter ersten Elektrode (A) aufweist.
  3. Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, daß besagter Körper (10) ein Kunststoffgehäuse umfaßt, wobei besagte erste Elektrode (A) innerhalb des Gehäuses an einem Ende des Gehäuses angebracht ist, besagte zweite Elektrode (B) innerhalb des Gehäuses an einer Position räumlich im wesentlichen von besagtem ersten Ende und von besagter ersten Elektrode (A) getrennt angeordnet ist.
  4. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, daß besagte zweite Elektrode (B) benachbart einer flachen unteren Wand besagten Gehäuses angebracht ist.
  5. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, daß besagte zweite Elektrode (B) eine flache Metallage oder -folie umfaßt, die benachbart besagter flachen unteren Wand des Gehäuses angeordnet ist.
  6. Vorrichtung nach Anspruch 2 in Kombination mit einer abnehmbaren und wiederanbringbaren Transferelektrode (16), wobei besagte Transferelektrode, wenn angepaßt, sich von der Nähe besagter zweiten Elektrode (B) zu besagtem einen Ende besagten Körpers erstreckt, wobei besagte Transferelektrode (16) ein elektrisch leitendes Element enthält, das an der Vorderwand besagten Körpers an einer Stelle benachbart zu besagter ersten Elektrode jedoch seitlich räumlich von derselben durch einen dielektrischen Zwischenraum getrennt endet, wobei die Anordnung so ist, daß, wenn besagte Transferelektrode angepaßt ist, ein Niedrigradiofrequenzimpedanzweg zwischen besagter zweiten Elektrode und besagtem elektrisch leitenden Element aufgebaut ist.
EP93916068A 1992-07-31 1993-07-14 Apparat und verfahren zum messen von feuchtigkeit Expired - Lifetime EP0653069B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB929216308A GB9216308D0 (en) 1992-07-31 1992-07-31 Moisture sensing method and apparatus
GB9216308 1992-07-31
PCT/GB1993/001475 WO1994003817A1 (en) 1992-07-31 1993-07-14 Moisture sensing method and apparatus

Publications (2)

Publication Number Publication Date
EP0653069A1 EP0653069A1 (de) 1995-05-17
EP0653069B1 true EP0653069B1 (de) 1997-04-23

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP93916068A Expired - Lifetime EP0653069B1 (de) 1992-07-31 1993-07-14 Apparat und verfahren zum messen von feuchtigkeit

Country Status (5)

Country Link
EP (1) EP0653069B1 (de)
AU (1) AU4577193A (de)
DE (1) DE69310180T2 (de)
GB (1) GB9216308D0 (de)
WO (1) WO1994003817A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2347220B (en) * 1999-02-23 2003-12-31 Rynhart Res Ltd A moisture meter
US7332716B2 (en) 2005-06-06 2008-02-19 Flir Systems Ab IR camera
NL2003163C2 (en) 2009-07-09 2011-01-11 Salusion Ip B V A moisture detecting module and a receiving unit.
ITUA20162704A1 (it) 2016-04-19 2017-10-19 Bitron Spa Dispositivo sensore per rilevare la presenza di una sostanza elettroconduttiva in una regione spaziale e sue applicazioni.

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4422035A (en) * 1981-12-11 1983-12-20 Extrude Hone Corporation Capacitance measurement probe
US4468610A (en) * 1982-04-14 1984-08-28 Penril Corp. Radio frequency apparatus for measuring moisture content of materials as a function of dielectric constant
GB2238622A (en) * 1989-11-15 1991-06-05 Electricity Council Sensing device

Also Published As

Publication number Publication date
DE69310180T2 (de) 1997-07-31
EP0653069A1 (de) 1995-05-17
WO1994003817A1 (en) 1994-02-17
DE69310180D1 (de) 1997-05-28
GB9216308D0 (en) 1992-09-16
AU4577193A (en) 1994-03-03

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